Computer users today have a wide variety of vehicles with which to view electronic documents. Desktop computers, laptop computers, pocket-sized computers, and tablet computers or just a few examples of the many different types of devices with which a user may view electronic documents. Each of these types of devices has a different form factor and displays documents slightly differently. For instance, a PDA has a very different viewable area than a monitor used with a desktop computer. The desktop computer probably has a different viewable area than the laptop computer. To compound the problem, electronic documents are created in very many different formats that may each have different viewing attributes.
Users are often presented with the problem that a particular document may display well on one device, such as a laptop computer, yet that document may not display well on another device, such as a PDA. Software developers have attempted to create a document format that is displayable on many different types of devices. For instance, a “reflowable” document representation, such as HTML, allowed for a certain amount of resizing when the window size changed without a serious detrimental impact on the layout of the document. However, using this format often hinders the document author's ability to control precisely how the document will appear. In addition, because reflowable documents are intended to be viewed somewhat well on many different devices, they do not necessarily provide an optimized viewing experience on any one device.
In contrast, formats that allow more control over how a document is displayed typically make the document applicable to a limited number of devices. For instance, a word processing document may be viewed on a desktop computer in a visually satisfactory manner. However, the word processing document, if displayed on a PDA may appear squished or otherwise inappropriate. In addition, a document created with a word processor for a particular size paper, such as letter-sized, may not print properly on another size paper, such as A4-sized.
Some document formats allow strict control over how the document is viewed by making the content of the document essentially a graphical image. One drawback of this document format is that several different versions of the entire document must be made available for each device upon which the document is intended to be viewed. In addition, the content of the fixed-format document is not editable.